Patients With Atopic Dermatitis Sensitized to Pet Dander Mount IgE and T-Cell Responses to Mammalian Cystatins, Including the Human Self-Protein.

BACKGROUND: Immediate and delayed-type hypersensitivity reactions to pet-borne allergens are common in atopic diseases. In atopic dermatitis (AD), controversy surrounds the contribution to the disease of cross-reactivity to self-proteins. Human cystatin A and the cat allergen Fel d 3 belong to the cystatins, an evolutionary conserved protein family. The objective of the present study was to assess crossreactivity between mammalian cystatins and to analyze T-cell responses to cystatin in AD patients sensitized to pet dander. METHODS: cDNA coding for dog cystatin was cloned from dog skin. Sera from 245 patients with IgE-mediated sensitization to cat and dog dander were tested for IgE binding to recombinantly expressed feline, canine, and human cystatin. Of these, 141 were also diagnosed with AD. RESULTS: Cystatin-specific IgE was detected in 36 patients (14.7%), of whom 19 were considerably affected by AD. Within the AD patients, 9 had measurable IgE against all 3 cystatins. Cystatin-sensitized AD patients did not differ from non-cystatin-sensitized patients in terms of disease severity, age, or total IgE levels. T-cell cytokine measurements showed elevated IL-4 levels after stimulation with feline and human cystatin. CONCLUSIONS: The humoral response suggests that in addition to Fel d 3, the homologous protein from dog might play a role in allergy. Furthermore, human cystatin appears to be capable of driving a type 2 immune response in sensitized AD patients and may therefore be considered a so-called autoallergen, as proposed for other evolutionary conserved proteins.

Patients With Atopic Dermatitis Sensitized to Pet Dander Mount IgE and T-Cell Responses to Mammalian Cystatins, Including the Human Self-Protein

Background: Immediate and delayed-type hypersensitivity reactions to pet-borne allergens are common in atopic diseases. In atopic dermatitis (AD), controversy surrounds the contribution to the disease of cross-reactivity to self-proteins. Human cystatin A and the cat allergen Fel d 3 belong to the cystatins, an evolutionary conserved protein family. The objective of the present study was to assess crossreactivity between mammalian cystatins and to analyze T-cell responses to cystatin in AD patients sensitized to pet dander. Methods: cDNA coding for dog cystatin was cloned from dog skin. Sera from 245 patients with IgE-mediated sensitization to cat and dog dander were tested for IgE binding to recombinantly expressed feline, canine, and human cystatin. Of these, 141 were also diagnosed with AD. Results: Cystatin-specific IgE was detected in 36 patients (14.7%), of whom 19 were considerably affected by AD. Within the AD patients, 9 had measurable IgE against all 3 cystatins. Cystatin-sensitized AD patients did not differ from non–cystatin-sensitized patients in terms of disease severity, age, or total IgE levels. T-cell cytokine measurements showed elevated IL-4 levels after stimulation with feline and human cystatin. Conclusion: The humoral response suggests that in addition to Fel d 3, the homologous protein from dog might play a role in allergy. Furthermore, human cystatin appears to be capable of driving a type 2 immune response in sensitized AD patients and may therefore be considered a so-called autoallergen, as proposed for other evolutionary conserved proteins. (AU)

Antecedentes: Las reacciones de hipersensibilidad de tipo inmediato y retardado a los alérgenos que están en las mascotas son comunes en las enfermedades atópicas. En este estudio, en pacientes con dermatitis atopica (DA), se analiza la reactividad cruzada con las autoproteínas y su contribución a la enfermedad. Tanto la cistatina A humana como el alérgeno felino Fel d 3 pertenecen a la familia de las cistatinas, una familia de proteínas conservadas evolutivamente. El objetivo del presente estudio fue evaluar la reactividad cruzada entre las cistatinas de mamíferos y analizar la respuestas de las células T a la cistatina en pacientes con DA sensibilizados a la caspa de las mascotas. Métodos: El ADNc que codifica la cistatina de perro se clonó a partir de piel de perro. Se analizaron sueros de 245 pacientes con sensibilización por IgE a la caspa de gato y perro para determinar la unión de IgE a cistatina felina, canina y humana expresada de forma recombinante, respectivamente. De estos 245 pacientes, 141 fueron diagnosticados de DA. Resultados: Se detectó IgE específica frente a cistatina en el 14,7% (36) de los pacientes, de los cuales 19 padecían DA. Dentro de los pacientes con DA, 9 tenían IgE medible contra las tres cistatinas. Los pacientes con DA sensibilizados frente a cistatina no difirieron de los pacientes no sensibilizados con cistatina en términos de gravedad de la enfermedad, edad o niveles totales de IgE. El análisis de citocinas de células T reveló niveles elevados de IL-4 después de la estimulación con cistatina felina y humana. Conclusión: La respuesta humoral sugiere que, además de Fel d 3, la proteína homóloga de perro también podría desempeñar un papel en la alergia. Además, la cistatina humana parece ser capaz de promover una respuesta inmune de tipo 2 en pacientes con DA sensibilizados y, por lo tanto, puede considerarse un autoalérgeno, como se ha propuesto para otras proteínas conservadas evolutivamente. (AU)

Human thioredoxin, a damage-associated molecular pattern and Malassezia-crossreactive autoallergen, modulates immune responses via the C-type lectin receptors Dectin-1 and Dectin-2.

Human thioredoxin (hTrx), which can be secreted from cells upon stress, functions in allergic skin inflammation as a T cell antigen due to homology and cross-reactivity with the fungal allergen Mala s13 of the skin-colonizing yeast Malassezia sympodialis. Recent studies have shown that cell wall polysaccharides of Malassezia are detected by the immune system via the C-type lectin receptors Dectin-1 and Dectin-2, which are expressed on myeloid cells. Therefore, this study aimed to investigate a putative interaction between Dectin-1, Dectin-2 and the allergens Mala s13 and hTrx. Stimulation of human monocyte-derived dendritic cells or macrophages with Mala s13 or hTrx resulted in remarkable secretion of IL-1ß and IL-23. Blocking experiments suggest that hTrx induces IL-23 by Dectin-1 binding and IL-1ß by binding to either Dectin-1 or Dectin-2. Regarding Mala s13, Dectin-1 appears to be involved in IL-1ß signaling. Interference of Syk kinase function was performed to investigate downstream signaling, which led to diminished hTrx responses. In our experiments, we observed rapid internalization of Mala s13 and hTrx upon cell contact and we were able to confirm direct interaction with Dectin-1 as well as Dectin-2 applying a fusion protein screening platform. We hypothesize that this cytokine response may result in a Th2/Th17-polarizing milieu, which may play a key role during the allergic sensitization in the skin, where allergen presentation to T cells is accompanied by microbial colonization and skin inflammation.